Process for the conversion of ferro-phosphortjs into ferric phosphate



Patented June 2, 1931 UNITED STATES PATENT OFFICE CONWAY, BARON VON GIRSEWNALD, AND S 'WEIDMANN, OF FRANKFORT-ON-THE- MAIN, GERMANY, ASSIGNORS TO AMERICAN LURGI CORPORATION, OF NEW YORK,

- N. Y., A CORPORATION OF NEW YORK PROCESS FOR THE CONVERSION OF FERRO-PI-IOSPHORUS INTO FERRIC PHOSPHATE (FePO4) BY ROASTING IN AIR OR OTHER GASES CONTAINING OXYGEN No Drawing. Application filed May 5, 1930, Serial No. 450,058, and in Germany May 29, 1929.

This invention relates to a process for the conversion of ferro-phosphorus into ferric phosphate (FePO by roasting in air or other gases containing oxygen. Considerable difiiculties are encountered in carrying out this process, since the oxidation is extremely slow. If, for example, finely ground ferrophosphorus having a phosphorus content of 24% is roasted in accordance with the usual methods in a muffle furnace at temperatures of for example, 700 to 800 (1, it is only pos sible, even in the presence of large amounts of moist air, to convert about 16% of the initial material into ferric phosphate during a roasting period of 10 hours.

It has been found in accordance with the junction such as for example, an alkali metal saltand an alkaline earth metal salt.

Example 5 kilograms of ferro-phosphoruscontain ing 24% P are mixed in a finely ground state with grams of sodium chloride, and the mixture is roasted in a mufile furnace at700 to 800 (3., in the presence of air. After a roasting period of only 6 hours, 85% of the ferro-phosphorus had been converted into ferric phosphate. At the end of the roasting process, traces only of chlorine can be detected in the roasted material.

In general, it has been found that the moisturepresent in the air is sufiicient, and cons sequently it is not necessary as a rule to increase the degree ofhumidity of the air.

We claim 1. A process for the production of ferric phosphate Which comprises treating ferrophosphorus at elevated temperature with oxygen-containing gases in the presence of a substance of the group consisting of alkali and alkaline earth metal compounds.

2. A process for the production of ferric phosphate which comprises treating ferrophosphorus at elevated temperatures with air in the presence of a relatively small amount of a compound of the group consisting of thewater-soluble alkali and alkaline earth metal compounds.

'8. A process for the production of ferric phosphate which comprises treating ferrophosphorus at elevated temperatures With oxygen-containing gases in the presence of an alkali metal compound.

4. A process for the production of ferric phosphate which comprises treating ferrophosphorus at elevated temperatures with oxygen-containing gases in the presence of a sodium compound. p p

5. A process for the production of ferric phosphate which comprises. treating ferrophosphorus at elevated temperatures with voxygen-containing gases in the presence of sodium carbonate.

6. A process for the production of ferric phosphate which comprises treating ferrophosphorus at elevated temperatures with air in the presence of a relatively small amount of a water-soluble alkali metalcompound.

7. A process for the production of ferric phosphate which comprises treating ferrophosphorus at elevated temperatures with air in the presence of a relatively small,

amount of sodium chloride.

In testimony whereof, we affix our signatures.

CONWAY BARON von GIRSEWALD. HANS WEIDMANN. 

